Underevaluated Solvent Effects in Electrocatalytic CO Reduction by Fe Chloride Tetrakis(pentafluorophenyl)porphyrin.

Fe chloride tetrakis(pentafluorophenyl)porphyrin (1) is known to have poor electrocatalytic activity for the CO -to-CO conversion in dimethylformamide. In this work, we re-examined Fe porphyrin 1 as a CO reduction catalyst in various solvents. Our results show that 1 displays fairly high electrocatalytic CO -to-CO activity in acetonitrile with a turnover frequency (TOF) up to 4.2×10  s . On the other hand, 1 shows a modest activity in propylene carbonate, and is inefficient to catalyze CO reduction in benzonitrile, dimethylformamide, and tetrahydrofuran. Several solvent effects were considered, but none of these effects alone can explain the observed large activity difference of 1 for CO reduction in these solvents. Based on the results, it is suggested that more care should be paid when comparing different CO reduction catalysts because solvent effects are significant and are underevaluated.